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Some Numbers – A 4⁰C World

In my last post I said I’d look into information available quantifying the effects of the level of climate change currently expected. I have to admit that I’ve spent a very frustrating morning trying to find facts and figures about the effects and have not managed to find a great deal, particularly relating to the effects of the 4 to 6 ⁰C increases that are forecast on current trends (of change and our response to date and planned).

Anyone reading who has another or better source of up to date facts and figures about what we are letting ourselves in for, please do comment at the bottom of this post.

Generally what I’ve found is that when looking at the higher end of the forecast increases in temperatures, commentary in the scientific papers falls back on statements to the effect of “it will be really bad” and comparing with the coldest temperatures during the last ice age (5-6 ⁰C lower than current temperatures).

I think the lack of quantification available is genuine. But I think some numbers would be better than none:

“Uncertainty is an argument for a more, not less, demanding goal [on reducing greenhouse gas emissions], because of the size of the adverse climate-change impacts in the worst-case scenarios.” – Stern, 2006

And taking that a step further, lack of figures on the impacts is an argument for a more, not less, demanding goal, because the figures that we do have, particularly for lower increases, are bad enough.

Anyway, on to what I have managed to unearth.

My main source is a paper published in January 2011 by the Royal Society. I’ll put links to the sources directly in the text below. To start, a 4 ⁰ C increase is estimated to be reached during 2070s.

Looking at water, it looks as though dry regions are to get dryer and wet regions are to get wetter. I found it difficult to interpret the graphs, but it appears to show a 30-70% decrease in the water available per capita, dependent on population growth and temperature change (the latter dominates in a 4 ⁰C world). The regions under the greatest water stress at the moment are the US, Mediterranean Europe, India and China, plus parts of Africa – and these are the areas that are expected to feel the brunt of increases in water stress in the coming decades. This is leading to increases in grain prices as water is used directly rather than for agriculture.

Looking at monetised costs, in Africa alone in 2030 for adapting to climate change are estimated at $60 billion per annum. This still leaves residual effects that cannot be avoided.

Costs for global sea-level rises for a 4 ⁰C world are expected to reach $37-407bn per annum (I’ve adjusted to show present value), with the range depending on whether 4 ⁰C leads to 50 cm or 2 m of rises, which in turn depends on the unknown extent of the melting of the Greenland ice sheet in those conditions.

The Stern Report of 2006 costs of mitigating climate change are -2% to +5% of GDP (the lower part of the range relating to more prompt and efficient mitigation action), with an average of 1% of GDP. Global consumption would decrease by 20% otherwise. Then the net benefits of one year’s action to mitigate climate change would be of the order of $2.5 trillion. So we should do so, you would think?

The UK parliament is currently discussing the Energy Bill. It falls short in that it doesn’t commit to a target on reducing greenhouse gas emissions, and so I urge you to take action to promote amendments to the bill to introduce an end target and interim targets. In developed nations, we need to largely decarbonise by 2030 for 37% chance of not exceeding 2 ⁰C (assuming developing nations peak their emissions by around 2025), according to the Royal Society.

The proposed changes to the bill not only give us a chance of mitigating climate change, they also make sound economic sense in the medium term. It is estimated that there would be a £23bn saving in the UK if we went for de-carbonisation rather than for emerging fossil fuel deposits. Gas prices (not renewables) were responsible for 62% of the increase in energy prices since 2004.

Again, if anyone reading has a different or better source of information about the quantification of the effects of a changing climate, then please do share by commenting below.

3 thoughts on “Some Numbers – A 4⁰C World”

Not longer after posting this I watched a video that claimed that Hurricane Sandy cost $65bn and the drought in the US last year cost $35bn. No, you can’t attribute all of that to climate change, but you can attribute a lot of it. Makes me think that the figures could be a lot worse than those in my post…